The energetic ions and DD neutrons from microfusion at the interelectrode space of a low energy nanosecond vacuum discharge with deuterium-loaded Pd anode has been demonstrated recently. To understand better the physics of fusion processes the detailed PIC simulation of the discharge experimental conditions have been developed using a fully electrodynamic code KARAT. The dynamics of main charge particle species was reconstructed in time and interelectrode space. The principal role of a virtual cathode (VC) and the corresponding single and double potential well formed in the interelectrode space are recognised. The calculated depth ϕ of the quasistationary potential well (PW) of the VC is about 50-60 kV, and the D + ions being trapped by this well accelerate up to energy values needed to provide collisional DD nuclear synthesis. Both experiment and PIC simulations illustrate very favourable scaling of the fusion power density at decreasing of VC radius ( ∼ ϕ 2 /r 4 V C ) for the chosen inertial electrostatic confinement fusion scheme based on miniature nanosecond vacuum discharge. Meanwhile, the initial stage of discharge is understood still poorly. When voltage is applied, the electron beam extracted from cathode starts to interact with the surface of deuterium-loaded Pd anode. This early stage of discharge manifests sometime the peaks registered by photomultipliers which are similar to neutron ones from time-of-flight measure under the study of collisional DD synthesis at the further stages of discharge. The detailed study of Pd anode surface morphology have been performed and recognized, in particular, the number of various pores and craters of different sizes. We remark that besides of rather usual craters (due to electron beams -anode interaction) some of the craters on the Pd anode surface may correspond to anode ectons (explosive centres) and consider their possible nature. Specifics of warm dense matter (WDM) generated at different stage of discharge is discussed. The data obtained are compared with recent results on initiation of DD reactions by electron beams at deuterium -loaded Pd foils and correspondent data on their surface morphology.

Neutrons from DD fusion in the interelectrode space of a table-top, low-energy, nanosecond vacuum discharge with a deuterium-loaded Pd anode have been demonstrated earlier. In addition, the principal role of a virtual cathode and the corresponding deep potential well formed in the interelectrode space are recognized under detailed particle-in-cell simulations of the discharge experimental conditions using a fully electrodynamic code. PIC modelling has allowed the identification of the scheme of small-scale experiments with a rather old branch of plasma physics as the inertial electrostatic confinement fusion. The goal of this work is to present and discuss in detail the available experimental results on deuteron oscillations followed by pulsating DD neutron yield in this scheme based on nanosecond vacuum discharge. PIC simulations of some experimental regimes of pulsating neutron yield are also shown and discussed, as well as comparisons with an available similar scheme of periodical oscillating plasmas spheres for fusion. KEYWORDS inertial electrostatic confinement, neutron yield, virtual cathode 1 Contrib. Plasma Phys. 2018;58:952-960 www.cpp-journal.org

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